The glass is falling, it seems (7)

I believe the answer is:

tumbler

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'the glass' is the definition.
(tumbler is a kind of glass)

I can't explain the remainder of the clue.

(Other definitions for tumbler that I've seen before include "One flips" , "that can clearly hold a drink" , "used to drink" , "Drinking glass or old acrobat" , "Glass for whisky" .)

I've seen this clue in the Evening Standard.

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